Tricky problem, Jsh. Faced it myself because I cannot get into crossovers/SUVs without danger of further knackering already busted discs in back. Also find the larger opening of two-door body easier to handle. Ended up with Mini hatch. Very happy with it but do not at present need to sling a ‘chair into rear seats. This would be impossible. It would work in the Mini convertible (hood down – all automatic and powered in alleged 20 secs). Only other options are Citroen C1, Peugeot 108, VW Up! and Ford (the Fiesta, promising in terms of space). Have discounted the Fiat 500 and Smart as too small in back. Problem with the non-Mini models is that they are all well underpowered. Best of them seems to be the Mhev Fiesta. Search on Motability list telling it show you 2/3-door cars.
There are some quite nice crossovers coming up (Mazda is one) with those excellent barn/suicide door pairs (like original Mini Clubman from BMW) which might deliver the goods if they make it on to scheme. Biggest problem overall is that more and more makers are no longer offering two- and/or three-door vehicles.